"One of the goals ... is to provide design guidance for selecting or creating the most appropriate architecture for a given application domain" #readingToday One of the goals of this dissertation is to provide design guidance for the task of selecting or creating the most appropriate architecture for a given application domain, keeping in mind that an architecture is the realization of an architectural design and not the design itself. An architecture can be evaluated by its run-time characteristics, but we would obviously prefer an evaluation mechanism that could be applied to the candidate architectural designs before having to implement all of them. Unfortunately, architectural designs are notoriously hard to evaluate and compare in an objective manner. Like most artifacts of creative design, architectures are normally presented as a completed work, as if the design simply sprung fully-formed from the architect's mind. In order to evaluate an architectural design, we need to examine the design rationale behind the constraints it places on a system, and compare the properties derived from those constraints to the target application's objectives.